Abstract:

A spinal implant comprising one or more integrated walls spaced apart to
define an interior cavity configured to retain bone graft material, and
having at least one aperture providing a pathway between the interior
cavity and an exterior environment of the implant; wherein at least one
of the one or more walls has a lumen therein, the lumen terminating at a
post-operatively accessible refill port and at one or more drug delivery
ports disposed in a surface of the at least one wall, and configured to
allow drugs to flow from the refill port to the one or more delivery
ports.

Claims:

1. A spinal implant comprising:one or more integrated walls spaced apart
to define an interior cavity configured to retain bone graft material,
and having at least one aperture providing a pathway between the interior
cavity and an exterior environment of the implant;wherein at least one of
the one or more walls has a lumen therein, the lumen terminating at a
post-operatively accessible refill port and at one or more drug delivery
ports disposed in an exterior surface of the at least one wall, and
configured to allow drugs to flow from the refill port to the one or more
delivery ports.

2. The spinal implant of claim 1, wherein the one or more integrated walls
collectively define top and bottom surfaces and load bearing members
extending between the top and bottom surfaces.

3. The spinal implant of claim 2, wherein the top and bottom surfaces are
each configured to contact one or more of bone and cartilage.

4. The spinal implant of claim 1, wherein the one or more integrated walls
define a substantially cylindrical vertebral body cage implant.

5. The spinal implant of claim 1, wherein the least one aperture comprises
a plurality of apertures formed in a spaced arrangement in the one or
more integrated walls.

6. The spinal implant of claim 5, wherein the one or more integrated walls
define a substantially cylindrical vertebral body cage implant, and
further wherein the at least one aperture comprises a plurality of
apertures circumferentially spaced around the cylindrical vertebral body
cage implant.

7. The spinal implant of claim 1, wherein the at least one wall has a
second lumen therein, the second lumen terminating at a second
post-operatively accessible refill port and has at one or more second
drug delivery ports disposed in an exterior surface of the at least one
wall, and configured to allow drugs to flow from the refill port to the
one or more second delivery ports.

8. The spinal implant of claim 1, wherein the refill port is configured to
securely and detachably connect to a catheter.

9. The spinal implant of claim 1, wherein the spinal implant is configured
to be implanted in at least one of a vertebral disc or a location of an
explanted disc.

10. The spinal implant of claim 1, wherein the spinal implant is a spinal
bone implant.

11. The spinal implant of claim 10, wherein the bone implant is a pedicle
screw.

12. The spinal implant of claim 10, wherein the bone implant is configured
to be implanted in the vertebral body.

13. The spinal implant of claim 1, wherein the flow rate through the one
or more drug delivery ports is externally controllable.

14. The spinal implant of claim 2, further comprising:an extension
configured to be detachably connected to the top surface of the one or
more integrated walls.

15. A bone implant comprising:one or more integrated walls spaced apart to
define an interior cavity configured to retain bone graft material, and
having at least one aperture providing a pathway between the interior
cavity and an exterior environment of the implant;wherein at least one of
the one or more walls has a lumen therein, the lumen terminating at a
post-operatively accessible refill port and at one or more drug delivery
ports disposed in an exterior surface of the at least one wall, and
configured to allow drugs to flow from the refill port to the one or more
delivery ports.

16. The bone implant of claim 15, wherein the one or more integrated walls
collectively define top and bottom surfaces and load bearing members
extending between the top and bottom surfaces.

17. The bone implant of claim 16, wherein the top and bottom surfaces are
each configured to contact one or more of bone and cartilage.

18. The bone implant of claim 15, wherein the one or more integrated walls
define a substantially cylindrical vertebral body cage implant.

19. The bone implant of claim 15, wherein the least one aperture comprises
a plurality of apertures formed in a spaced arrangement in the one or
more integrated walls.

20. The bone implant of claim 19, wherein the one or more integrated walls
define a substantially cylindrical vertebral body cage implant, and
further wherein the at least one aperture comprises a plurality of
apertures circumferentially spaced around the cylindrical vertebral body
cage implant.

21. The bone implant of claim 15, wherein the at least one wall has a
second lumen therein, the second lumen terminating at a second
post-operatively accessible refill port and has at one or more second
drug delivery ports disposed in an exterior surface of the at least one
wall, and configured to allow drugs to flow from the refill port to the
one or more second delivery ports.

22. The bone implant of claim 15, wherein the refill port is configured to
securely and detachably connect to a catheter.

23. The bone implant of claim 15, wherein the bone implant is a spinal
bone implant.

24. The bone implant of claim 15, wherein the bone implant is a pedicle
screw.

25. The bone implant of claim 15, wherein the bone implant is configured
to be implanted in the vertebral body.

26. The bone implant of claim 15, wherein the flow rate through the one or
more drug delivery ports is externally controllable.

27. The bone implant of claim 16, further comprising:an extension
configured to be detachably connected to the top surface of the one or
more integrated walls.

28. A spinal implant system comprising:a spinal implant having:one or more
integrated walls spaced apart to define an interior cavity configured to
retain bone graft material, and having at least one aperture providing a
pathway between the interior cavity and an exterior environment of the
implant,wherein at least one of the one or more walls has a lumen
therein, the lumen terminating at a post-operatively accessible refill
port and at one or more drug delivery ports disposed in an exterior
surface of the at least one wall, and configured to allow drugs to flow
from the refill port to the one or more delivery ports; anda drug source
fluidically coupled to the refill port of the spinal implant.

29. The implant system of claim 28, wherein the drug source comprises:an
injection port configured to receive a needle therein.

33. The implant system of claim 28, wherein the one or more integrated
walls collectively define top and bottom surfaces and load bearing
members extending between the top and bottom surfaces.

34. The implant system of claim 28, wherein the one or more integrated
walls define a substantially cylindrical vertebral body cage implant.

35. The implant system of claim 28, wherein the at least one wall has a
second lumen therein, the second lumen terminating at a second
post-operatively accessible refill port and has at one or more second
drug delivery ports disposed in an exterior surface of the at least one
wall, and configured to allow drugs to flow from the refill port to the
one or more second delivery ports.

36. The implant system of claim 28, wherein the refill port is configured
to be fluidically coupled to the drug source via a catheter.

37. The implant system of claim 36, wherein the catheter is detachable
connected to the refill port.

38. The implant system of claim 28, wherein the drug source is externally
replenishable.

39. The implant system of claim 28, wherein the spinal implant is a spinal
bone implant.

40. The implant system of claim 39, wherein the bone implant is a pedicle
screw.

41. The implant system of claim 28, wherein the flow rate through the one
or more drug delivery ports is externally controllable.

42. The implant system of claim 29, further comprising:an extension
configured to be detachably connected to the top surface of the one or
more integrated walls.

43. A method of using a spinal implant comprising one or more integrated
walls spaced apart to define an interior cavity configured to retain bone
graft material, and having at least one aperture providing a pathway
between the interior cavity and an exterior environment of the implant,
wherein at least one of the one or more walls has a lumen therein, the
lumen terminating at a post-operatively accessible refill port and at one
or more drug delivery ports disposed in an exterior surface of the at
least one wall, the method comprising:implanting the spinal implant into
a vertebral body of a patient;fluidcally coupling the refill port to a
drug source; anddelivering drugs from the drug source to the refill port
to facilitate the flow of drugs from the refill port to the one or more
delivery ports.

[0003]The present invention relates generally to medical implants, and
more specifically, to a replenishable drug delivery implant for bone and
cartilage.

[0004]2. Related Art

[0005]Certain conditions, defects, deformities and injuries may lead to
structural instabilities, in a patient's bone, cartilage or other
connective tissue. Such structural instability is particularly
problematic in a patient's spinal column due to the potential for nerve
or spinal cord damage, pain and other manifestations. FIG. 1 is a
perspective view of a segment 100 of a human spinal column. An
individual's spinal column (sometimes referred to as the vertebral
column) extends from the person's skull (not shown) to the pelvis (also
not shown) and consists of 33 individual bones known as vertebrae 102.
Two such vertebrae 102 are illustrated in FIG. 1. Between each vertebra
102 is a soft, gel-like cushion known as an intervertebral disc 104 which
absorbs pressure and prevents vertebrae 102 from contacting each other.
There are two such intervertebral discs 104 illustrated in FIG. 1. Each
vertebra 102 is held to other vertebrae in the spinal column by ligaments
(not shown) which also connect t vertebrae 102 to the individual's
muscles. Additional tendons (not shown) also fasten muscles to vertebrae
102.

[0006]Each vertebra 102 comprises a centrum or vertebral body 106
comprised of dense cortical bone forming the anterior portion of vertebra
102. Vertebral bodies 106 collectively provide structural support to the
spinal column. Posterially extending from vertebral body 106 is a spinous
process 122 and two transverse processes 120 on opposing lateral sides of
spinous process 122. The portion of vertebra 102 which extends between
transverse processes 120 and which is disposed between transverse
processes 120 and vertebral body 106 is referred to as pedicle 118.
Processes 120,122 add structural rigidity, assist in articulation of
vertebrae 102 in conjunction with the individual's ribs (not shown), and
serve as muscle attachment points.

[0012]Certain procedures use implants positioned in the patient's spinal
bone or cartilage, collectively and generally referred to as spinal
implants herein, to effect or augment the biomechanics of a patient's
spine. One common type of spinal implant that is used following
corpectomy or vertebrectomy is a vertebral body implant which is
positioned in a patient's vertebral body 106. Currently, there are a wide
number of available vertebral implants of varying design and material.
One class of vertebral body implant is configured to directly replace the
excised vertebra/ae. Another class of vertebral body implant is
configured for insertion into the intervertebral space in a collapsed
state and then expanded to contact adjacent vertebrae. The use of
expandable implants may be advantageous since a smaller incision is
required to insert the implant into the intervertebral space.
Additionally, expandable implants may assist with restoration of proper
loading to the spinal anatomy. Implants which include insertion and
expansion members that have a narrow profile, may also provide clinical
advantages. In some circumstances, it is desirable to have vertebral
endplate contacting surfaces that effectively spread loads across the
vertebral endplates. Vertebral body implants may also include a member
for maintaining the desired positions, and in some situations, being
capable of collapsing. Fusion implants including one or more openings may
also be advantageous because they allow for vascularization and bone
growth through the implant.

[0013]The implant commonly used following a discectomy is an interbody
fusion device, also referred to in the art as a cage. Conventional cage
designs have a cylindrical or rectangular shape, supporting walls, and a
hollow interior space for receiving grafting materials. Cylindrical cages
typically have threads along their entire length, whereas rectangular
cages have serrated anchors on the upper and lower surfaces. Threaded
cylinders usually have small pores and graft material is located inside
the hollow interior of the cylinder. The rigid hollow design of fusion
cages provide sufficient construct stiffness in arthrodesis and affords a
substantial stability for the motion segments after spinal surgery, as
well as shielding stress on the implanted graft. Boden S, et al., Spine
20:102 S-112S (1995); Silva M J, et al., Spine, 22(2):140-150 (1997).
Commercially available interbody fusion devices comprising threaded cages
include, for example, the BAK series of interbody fusion devices
available from Zimmer Spine Inc, Minneapolis, Minn.), and the INTERFIX
Threaded Fusion Device (by Medtronic Sofamor Danek, Memphis, Tenn.); BAK
is a registered trademark of Zimmer Spine Inc.

SUMMMARY

[0014]In one aspect of the present invention a spinal implant is provided.
The spinal implant comprises: one or more integrated walls spaced apart
to define an interior cavity configured to retain bone graft material,
and having at least one aperture providing a pathway between the interior
cavity and an exterior environment of the implant; wherein at least one
of the one or more walls has a lumen therein, the lumen terminating at a
post-operatively accessible refill port and having one or more drug
delivery ports disposed in an exterior surface of the at least one wall,
and configured to allow drugs to flow from the refill port to the one or
more drug delivery ports.

[0015]In another aspect of the present invention a bone implant is
provided. The bone implant comprises: one or more integrated walls spaced
apart to define an interior cavity configured to retain bone graft
material, and having at least one aperture providing a pathway between
the interior cavity and an exterior environment of the implant; wherein
at least one of the one or more walls has a lumen therein, the lumen
terminating at a post-operatively accessible refill port and having one
or more drug delivery ports disposed in an exterior surface of the at
least one wall, and configured to allow drugs to flow from the refill
port to the one or more delivery ports.

[0016]In another aspect of the present invention a spinal implant system
is provided. The spinal implant system comprises: a spinal implant
having: one or more integrated walls spaced apart to define an interior
cavity configured to retain bone graft material, and having at least one
aperture providing a pathway between the interior cavity and an exterior
environment of the implant, wherein at least one of the one or more walls
has a lumen therein, the lumen terminating at a post-operatively
accessible refill port and having one or more drug delivery ports
disposed in an exterior surface of the at least one wall, and configured
to allow drugs to flow from the refill port to the one or more delivery
ports; and a drug source fluidically coupled to the refill port of the
spinal implant.

[0017]In another aspect of the present invention, a method of using a
spinal implant comprising one or more integrated walls spaced apart to
define an interior cavity configured to retain bone graft material, and
having at least one aperture providing a pathway between the interior
cavity and an exterior environment of the implant, wherein at least one
of the one or more walls has a lumen therein, the lumen terminating at a
post-operatively accessible refill port and having one or more drug
delivery ports disposed in an exterior surface of the at least one wall
is provided. The method comprises: implanting the spinal implant into a
vertebral body of a patient; fluidically coupling the refill port to a
drug source; and delivering drugs from the drug source to the refill port
to facilitate the flow of drugs from the refill port to the one or more
delivery ports.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018]Illustrative embodiments of the present invention are described
herein with reference to the accompanying drawings, in which:

[0019]FIG. 1 is a perspective view of a segment of a human spinal column;

[0020]FIG. 2 is a perspective view of a vertebral body implant in
accordance with embodiments of the present invention;

[0021]FIG. 3 is a top view of a vertebral body implant illustrated in FIG.
2;

[0022]FIG. 4 is a cross-sectional view of the vertebral body implant
illustrated in FIG. 2 taken along section line 4-4;

[0023]FIG. 5 is a cross-sectional view of the vertebral body implant
illustrated in FIG. 2 taken along section line 5-5;

[0024]FIG. 6 is a cross-sectional view of the vertebral body implant
illustrated in FIG. 2 taken along section line 6-6;

[0025]FIG. 7 is a cross-sectional view of the vertebral body implant
illustrated in FIG. 2 taken along section line 7-7;

[0026]FIG. 8A is a perspective view of an alternative embodiment of the
vertebral body implant illustrated in FIG. 2 depicted with an extension
that, when joined to the vertebral body implant, increases the length of
the implant, in accordance with embodiments of the present invention;

[0027]FIG. 8B is a perspective view of the vertebral body implant and
extension illustrated in FIG. 8A joined together, in accordance with
embodiments of the present invention;

[0028]FIG. 8C is a cross-sectional view of the vertebral body implant and
extension illustrated in FIG. 8B taken along section line 8C-8C;

[0029]FIG. 9 is a side view of a pedicle screw in accordance with
embodiments of the present invention;

[0030]FIG. 10 is a cross-sectional view of the pedicle screw illustrated
in FIG. 9 taken along section line 10-10;

[0031]FIG. 11 is a top view of an implanted arrangement of two pedicle
screws illustrated in FIG. 9, in accordance with embodiments of the
present invention;

[0032]FIG. 12 is a perspective view of the vertebral body implant
illustrated in FIG. 2 implanted in a vertebral body, in accordance with
embodiments of the present invention;

[0033]FIG. 13 is a side view of a cartilage implant implanted in the
intevertebral disc adjacent the human pelvis, in accordance with
embodiments of the present invention;

[0034]FIG. 14 is a flowchart illustrating a method for implanting an
embodiment of a vertebral body implant in accordance with embodiments of
the present invention; and

[0035]FIG. 15 is a perspective view of a spinal implant system in
accordance with embodiments of the present invention.

DETAILED DESCRIPTION

[0036]Aspects and embodiments of the present invention are directed to a
medical implant implantable in the cartilage or bone of a patient to
provide long-term replenishable local administration of a drug to the
bone or cartilage at the implant site. Embodiments of the present
invention are described below with reference to medical implants
implantable in the bone and cartilage of the spinal column. Such implants
are generally and collectively referred to herein as spinal implants.

[0037]Referring to FIG. 1, vertebral corpectomy is a surgical procedure
that involves removing a portion of a vertebral body 106 in cases of, for
example, trauma, infection (osteomyelitis), and spinal metastases, etc. A
discectomy is a surgical procedure in which the central portion of an
intervertebral disc 104, the nucleus pulposus, is removed. A discectomy
is often performed in connection with a vertebral corpectomy, although
there are a variety of degenerative and other diseases of intervertebral
discs 104 which may require a discectomy. A pathological fracture or
surgical resection of a vertebral body 106 or intervertebral disc 104
adversely affects the ability of the bone or disc to structurally support
the patient's spinal column. As such, corpectomies and discectomies
usually require reconstruction of the resected portion of the vertebra
102 or disc 104.

[0038]Certain aspects and embodiments of the present invention are
generally directed to an improved spinal implant, a vertebral body
implant that restores the biomechanical integrity of the spinal column
while enabling in vivo delivery of drugs to vertebral body 106. Regarding
the restoration of biomechanical integrity, embodiments of the vertebral
body implant are constructed to contact the intervertebral disc 104 or
vertebra 102 above and below the corpectomized vertebra 102, and to
structurally transfer the load placed on the implant. In some
embodiments, the vertebral body implant retains bone growth promoting
materials which interface with vertebral body 106 to strengthen the bone
and/or to integrate the vertebral body implant into the vertebral body.

[0039]Regarding the in vivo delivery of drugs to the vertebral body,
embodiments of the vertebral body implant of the present invention may be
used to deliver a range of different synthetic or naturally occurring
pharmaceutical or biological agents (collectively and generally referred
to as `drugs" herein) in liquid or gel formulations depending upon the
particular application. Such drugs may be administered for any actual or
potential therapeutic, prophylactic or other medicinal purpose.
Representative examples of drugs which may be released from embodiments
of a bone or cartilage implant of the present invention include but are
not limited to analgesics, anesthetics, antimicrobial agents, antibodies,
anticoagulants, antifibrinolytic agents, anti-inflammatory agents,
antiparasitic agents, antiviral agents, cytokines, cytotoxins or cell
proliferation inhibiting agents, chemotherapeutic agents, radiolabeled
compounds or biologics, hormones, interferons, and combinations thereof.
Thus, it is contemplated that implants of the present invention may be
used to deliver a formulation comprising an agent used in chemotherapy,
radiotherapy (brachytherapy or a radioactive substrate including, but not
limited, to a liquid or gel).

[0040]Alternatively, implants of the present invention may used to deliver
drug(s) used in the management of pain and swelling that occurs following
the implantation surgery. For example, an implant may release an
effective amount of an analgesic agent alone or in combination with an
anesthetic agent. As yet another alternative, the implants of the present
invention may used to deliver drug(s) which help minimize the risk of
infection following implantation. For example, the implant may release a
therapeutic or prophylactic effective amount one or more antibiotics (for
example, cefazolin, cephalosporin, tobramycin, gentamycin, etc.) and/or
another agent effective in preventing or mitigating biofilms (for
example, a quorum-sensing blocker or other agent targeting biofilm
integrity). Bacteria tend to form biofilms on the surface of implants,
and these biofilms, which are essentially a microbial ecosystem with a
protective barrier, are relatively impermeable to antibiotics.
Accordingly, systemically administered antibiotics may not achieve
optimal dosing where it is most needed. However, embodiments of the
implant enable the delivery of the desired dose of antibiotic precisely
when and where needed. In certain circumstances, the antibiotic may be
delivered beneath the biofilm.

[0041]Certain embodiments of the bone and cartilage implants of the
present invention are adapted for use in the treatment of bone
metastases, and in specific embodiments of a spinal implant, spinal
metastases. In such embodiments, the spinal implant is configured to
deliver pharmacological compounds or other drugs used in the treatment of
spinal metastases. As noted, spinal metastases are treated surgically by
resection, resulting in the removal of significant amounts of bone and
soft tissue. Care must also be taken during resection to avoid spilling
the tumor d which may cause seeding of tumor cells into surrounding
tissue. Embodiments of the spinal implant are configured to locally
release one or more chemotherapeutic agents into the surrounding tissue
following implantation into vertebra 102 to destroy tumor cells remaining
at the surgical site following resection. Utilization of a spinal implant
of the present invention may be as a complement or replacement for the
systemic chemotherapy and/or radiation therapy that typically is
prescribed for such a patient.

[0042]As noted above, embodiments of the spinal implant may be used to
deliver one or a combination of therapeutic agents, including
chemotherapeutic agents (for example, paclitaxel, vincristine,
ifosfamide, dacttinomycin, doxorubicin, cyclophosphamide, and the like),
bisphosphonates (for example, alendronate, pamidronate, clodronate,
zoledronic acid, and ibandronic acid), analgesics (such as opoids and
NSAIDS), anesthetics (for example, ketoamine, bupivacaine and
ropivacaine), tramadol, and dexamethasone. In other variations of these
embodiments, the implant is useful for delivering an agent useful in
radiotherapy (brachytherapy or a radioactive substrate).

[0043]Thus, as an alternative to systemic administration of radioactive
agents that are capable of targeting a particular tissue, antigen, or
receptor type, these radioactive agents are administered locally
following implantation of the implant of the present invention. Such
radiotherapy agents include radiolabeled antibodies, radiolabeled peptide
receptor ligands, or any other radiolabeled compound capable of
specifically binding to the specific targeted cancer cells.

[0044]FIGS. 2-7 are different views of embodiments of a bone or cartilage
implant of the present invention. Specifically, FIGS. 2-7 illustrate
embodiments of a spinal implant for implantation in vertebral body 106
(FIG. 1) of a vertebra 102 (FIG. 1), referred to herein as vertebral body
implant 200. In accordance with the teachings of the present invention,
vertebral body implant 200 may be used to provide long-term,
replenishable delivery of drugs to vertebral body 106 of the vertebra 102
in which it is implanted.

[0045]Vertebral body implant 200 comprises a wall 202 configured to
encircle or enclose a volume of space referred to herein as interior
cavity 204. In the illustrative embodiments of FIGS. 2-7, vertebral body
implant 200 is a unitary structure; that is, it is formed of a single
cylindrical wall 202. It should be appreciated that in alternative
embodiments vertebral body implant 200 may be formed of a plurality of
integrated walls 202 spaced from each other to form interior cavity 204.

[0046]Interior cavity 204 is configured to retain osteogenic or bone
growth promoting materials (collectively and generally referred to herein
as bone growth promoting materials; not shown in FIGS. 2-7). Bone growth
promoting materials which may be loaded into interior cavity 204 include,
but are not limited to, bone morphogenic protein (BMP), bone graft
material, bone chips or bone marrow, synthetic or natural autograft,
allograft, xenograft, synthetic and natural bone graft substitutes such
as bioceramics and polymers, osteoinductive factors, a demineralized bone
matrix (DBM), mesenchymal stem cells, a LIM mineralization protein (LMP),
or any other suitable bone growth promoting material or substance that
would occur to one of skill in the art. It would be appreciated that the
bone growth promoting material may be used with or without a suitable
carrier to aid in maintaining the material within the device. These
carriers can include collagen-based carriers, bioceramic materials, such
as BIOGLASS, hydroxyapatite and calcium phosphate compositions; BIOGLASS
is a registered trademark of the University of Florida, Gainesville Fla.
The carrier material may be provided in the form of a sponge, a block,
folded sheet, putty, paste, graft material or other suitable forms. The
bone growth promoting material may be provided in a composition that
includes an effective amount of a bone morphogenetic protein (BMP),
transforming growth factor βI, insulin-like growth factor I,
platelet-derived growth factor, fibroblast growth factor, LIM
mineralization protein (LMP), and combinations thereof or other
therapeutic or infection resistant agents. Additionally, the bone growth
promoting material may be resorbable or nonresorbable. Examples of
resorbable materials that may be used include, but are not limited to,
polylactide, polyglycolide, tyrosine-derived polycarbonate,
polyanhydride, polyorthoester, polyphosphazene, calcium phosphate,
hydroxyapatite, bioactive glass, and various combinations thereof.

[0047]A manual access opening 214 in vertebral body implant 200 provides
the ability of a surgeon or other medical professional to manually access
interior cavity 204 to, for example, place bone growth promoting material
into the cavity. Access opening 214 may have any form suitable for the
dimensions of the implant, the viscosity of the bone growth promoting
material, and other factors. In the embodiment illustrated in FIG. 2,
unitary wall 202 is does not form a concentric circle, but rather
contains a discontinuity therein defining opening 214. Additionally, wall
204 has a top surface 208 and a bottom surface 210 configured to abut
cartilage and/or bone when implanted in a patient. In certain embodiments
top and/or bottom surfaces 208 and 210 have a surface finish or surface
features which facilitate placement and/or prevent lateral movement or
dislodgement of the implant during implantation. In the embodiments
illustrated in FIGS. 2-7, these surface features comprise surface domes
212 on top surface 208.

[0048]A plurality of apertures 206 are disposed in wall 202. Apertures 206
each provide an open pathway through which interior cavity 204
communicates with an exterior environment 216 of implant 200. In the
embodiments illustrated in FIGS. 2-7, five (5) apertures 206 are
circumferentially spaced around cylindrical wall 202. It should be
appreciated, however, that more or fewer apertures may be provided in
other embodiments. Furthermore, such aperture(s) 206 may have any
dimensions suitable for enabling the bone growth promoting material
retained in interior cavity 204 to interact with bone, which is proximate
to implant 200, and which do not compromise the intended function of the
implant. For example, in exemplary vertebral body implant 200 of FIGS.
2-7, wall(s) 204 are constructed and arranged such that the portions of
wall 202 extending between top and bottom surfaces 208, 210, and which
are laterally adjacent to apertures 206, referred to below as load
bearing members 218, are capable of bearing the load placed on top
surface 208 of implant 200, thereby retaining the structural integrity
necessary to support the spinal column.

[0051]In these embodiments, two drug delivery networks are independent of
each other. That is, as shown in FIGS. 4-7, the two drug delivery
networks are not fluidically coupled to each other. As such, drugs
introduced into refill port 222A will travel only through lumen 402A and
be delivered only via ports 220A. Similarly, a drug introduced into
refill port 222B will travel only through lumen 402B and will be
delivered only via ports 220B. Implementing multiple drug delivery
networks in a single bone or cartilage implant provides for the
independent administration of multiple drugs. In addition, each such
independent drug delivery network may be coupled to a different source of
such drugs.

[0052]In the embodiments illustrated in FIGS. 2-7, lumens 402A and 402B
are each a contiguous lumen traveling through load bearing members 218 as
well as the top member 224 and bottom member 226 of implant 200. It
should be appreciated that in alternative embodiments there may be a
single drug delivery network, implemented in the bone or cartilage
implant. It should also be appreciated that the network may be located in
any portion of the implant suitable for delivering a therapeutic dosage
of a selected drug to a target location.

[0053]Drug delivery ports 220 may be disposed on top surface 208, bottom
surface 210, lateral surface 211, and aperture surfaces 228. It should be
appreciated, however, that any such surfaces may have no drug delivery
ports 220. The distribution of ports 220 may be achieved at the time of
fabrication or following fabrication by occluding specific ports with,
for example, a plug or epoxy.

[0054]Additionally, the size of drug delivery ports may vary. In certain
embodiments, drug delivery ports 220 may have a diameter of approximately
250-500 microns. Drug delivery ports 220 of this size may be expected to
provide optimal bone ingrowth. In one embodiment, to provide further bone
ingrowth, a portion, e.g., a portion of the tissue- or bone-mating
surfaces, of the prosthesis is porous. Thus, the porous portion is a
tissue-contact surface that facilitates ingrowth and provides stable
fixation of the implant in the body. In another embodiment, the entire
surface of implant 200 is porous.

[0055]As noted, implant 200 comprises refill ports 222 through which drugs
may be introduced and reintroduced into implant 200. In certain
embodiments, refill ports 222 are configured to be detachably connected
to a catheter (not shown), the opposing end of which is fluidically
connected to a drug source such as a syringe port, an active drug or
programmable infusion device, or a passive drug infusion device. As
noted, refill ports 222 communicate with a respective lumen which, in
turn, communicates with a plurality of drug delivery ports 220 located at
selected locations on the surface of implant 200. The lumens may
optionally contain a porous inner substrate (not shown) such as silica or
polymer beads tailored to facilitate diffusion of a drug.

[0056]In certain embodiments, wall 202 of implant 200 may be formed of, be
coated with, or otherwise comprise a biocompatible material selected from
metals, polymers, ceramics, and combinations thereof. Typically,
embodiments of the present invention are non-biodegradable since the
implant is intended to function in a patient for an extended period,
preferably for the life of the patient. For instance, in certain
embodiments, wall 202 of implant 200 may be formed from a stainless
steel, a chrome-cobalt alloy, a titanium alloy, a ceramic, an ultra high
molecular weight polyethylene (e.g., a highly cross-linked, UHMW
polyethylene), or PEEK and PEEK composites. In other embodiments, the
implant is formed of or includes a ceramic (e.g., alumina, silicon
nitride, zirconium oxide), a semiconductor (e.g., silicon), a glass
(e.g., Pyrex, BPSG), or a degradable or non-degradable polymer; Pyrek is
a trademark of Corning Inc, New York.

[0057]In the embodiments of FIGS. 2-7, vertebral body implant 200 is, as
noted above, cylindrical in shape. However, it would be appreciated by
those or ordinary skill in the art that implant 200, or other bone and
cartilage implants of the present invention, may have other shapes and
sizes which also provide the requisite mechanical support. Exemplary
shapes include, for example, a rectangle, sphere, dome, or other shape.

[0058]Vertebral body implant 200 may be one of a plurality of vertebral
body implants each dimensions to accommodate a particular corpectomy or
vertebra size. In such embodiments the surgeon will have the opportunity
select the vertebral body implant having the size most appropriate for
the particular corpectomy. However, in certain circumstances, surgical
resection may result in the removal of relatively large regions of a
vertebral body 106 such an implant may not properly fit with the resected
region. For example, a selected implant 200 may be too small to provide
the desired structural support and the top surface 208 and bottom surface
210 of vertebral body implant 200 are unable to simultaneously contact
vertebra 102 or disc 104 immediately above and below the resected region.
FIGS. 8A-8C are perspective and cross-sectional views of other
embodiments of the present invention configured to resolve such sizing
issues.

[0059]In the embodiments illustrated in FIGS. 8A-8C, an extension 804 is
provided for attachment to top surface 208. Extension 804 has a
cross-sectional profile which is the same as the cross-sectional profile
of implant 200. In addition, an interlocking mechanism may be provided to
facilitate the secure joining of extension 804 to vertebral body implant
200. In the illustrative embodiments shown in FIGS. 8A-8C, the
interlocking mechanism is implemented as one or more snap-fit connectors
807 each comprising one or more snap-fit extensions 806 extending from
extension 804, and one or more corresponding snap-fit receptacles 808
within top surface 210 of implant 200. Snap-fit receptacles 808 are each
configured to receive and mate with a snap-fit extension 806 causing
extension 804 to be securely joined to implant 200. This is best
illustrated in FIG. 8B. In the illustrative embodiments, two snap-fit
connectors 807 are located on opposing sides of the surfaces of extension
804 and implant 200.

[0060]It should be appreciated that additional extensions may be added to
the implant illustrated in FIG. 8B. This is illustrated by the snap-fit
receptacles 808 disposed in top surface 820 of implant extension 804.

[0061]In the embodiments shown in FIGS. 8A-8C, extension 804 has lumens
810 and drug delivery ports 812 which operate substantially similar to
the lumens and ports described above with reference to FIGS. 2-7. As
shown in FIG. 8C, in certain embodiments, drug-delivery ports 220A and
220B on top surface 208 are configured to aligned with ports on the
bottom surface of extension 804. As such, lumens 402A and 402B are
aligned with, and fluidically coupled to, lumens 810A, 810B in extension
804 so that drugs may be delivered through ports 812.

[0062]As noted above, tope surface 208 may have surfaces domes 212
disposed thereon. As shown in FIG. 8C, surface domes 212 on top surface
208 of implant 200 are aligned and mate with corresponding surface
dimples 830 in the bottom surface of extension 804 to insure there is a
flush mating surface between implant 200 and extension 804.

[0063]FIG. 9 is a side view of an alternative embodiment of the present
invention implemented as a pedicle screw 900. FIG. 10 is cross-sectional
view of pedicle screw 900 of FIG. 9, taken along cross-sectional line
10-10. In the illustrative embodiments, each pedicle screw comprises a
refill port 902, lumen 906 and drug delivery ports 904. These elements of
pedicle screw 900 function substantially similar to the analogous
elements described above with reference to vertebral body implant 200.

[0064]As is well-known in the art, pedicle screws are typically
implemented as a part of a larger implantable structural support system.
FIG. 11 illustrates two pedicle screws 900 of FIGS. 9-10 each inserted
into pedicle 118 of a vertebra 102. As shown, screws 900 are connected to
one another by a cross plate 1102 forming part the larger structural
support system.

[0065]As noted above, vertebral body implant 200 may be configured for
bone ingrowth, or may have surface features which prevent movement of the
implant. In certain circumstances, additional stabilization of vertebral
body implant 200 is desired. FIG. 12 illustrates an embodiment in the
additional stabilization is provided by a biocompatible, photo-initiated
polymer rod or plate 1244. In this illustrative arrangement, plate 1244
is secured to vertebral body implant 200, as well as healthy vertebrae
above and below the damaged site. As shown, plate 1244 is secured to the
healthy vertebrae by screws 1242. Additionally, guide plates may be
provided for drilling holes to affix plate 1244 and/or rods to the
vertebrae with the necessary screws. Such screws may be bone screws or
pedicle screws, such as pedicle screws 900 of FIGS. 9-11. In specific
cases, the additional stabilization may employ currently available rigid
devices for such purposes with screws that are compliant or
non-compliant. An example of a suitable screw and plate fixation device
which may used with the present invention is the Kaneda Device (by
DePuy-Acromed, Cleveland Ohio).

[0066]FIG. 13 illustrates another bone and cartilage implant of the
present invention, shown as cartilage implant 1300. Cartilage implant
1300 is configured similar to implant 200 described above, but is
dimensioned to be implanted in a resected region of an intervertebral
disc. In the specific embodiment of FIG. 13, cartilage implant 1300 is
dimensioned to be positioned in resected region 1306 of an intervertebral
disc adjacent pelvis 1330. In the perspective illustrated in FIG. 13, a
refill port 1302 and drug deliver ports 1304 are visible.

[0067]FIG. 14 is a flowchart illustrating a method 1400 for using a spinal
implant, and particularly a vertebral body implant, in accordance with
embodiments of the present invention. At block 1402, a surgeon exposes a
damaged vertebral body of the patient. Exposing the vertebral body
includes administering general anesthesia to the patient, and properly
positioning the patient for access to the damaged vertebral body. A
standard anterior thoracic or lumbar approach, or a lateral extracavitary
approach may then be used to expose the vertebral body.

[0068]At block 1402, the surgeon provides a location for implantation of
the vertebral body implant. This may include performing a corpectomy by
use of a drill or bone ronguers to remove damaged bone. In such
embodiments, this step further includes ensuring that the proper amount
of bone has been removed by checking the depth of the newly created
corpectomy cavity using a marker and intraoperative X-ray. Once the
desired depth is achieved, osteotomes and a drill with cutting burr are
used to enlarge the corpectomy cavity. Under fluoroscopic guidance,
distraction is applied to the vertebral bodies above and below the
corpectomy cavity, and a ruler is used to measure the corpectomy cavity
to ensure that the cavity is a proper size to receive the vertebral body
implant.

[0069]At block 1406, the vertebral body implant is implanted into the
corpectomy cavity. Prior to implantation, morsellized bone allograft or
calcium triphosphate, prepared as per protocol, is placed into the
interior of the vertebral body implant. The vertebral body implant is
then impacted into the corpectomy cavity using tamps and a mallet, and
then countersunk to sit into the midportion of the cavity. Fluoroscopic
or other imaging may be used to ensure that the vertebral body implant is
properly positioned. Once this is completed, distraction of the vertebral
bodies above and below the corpectomy cavity is released.

[0070]At block 1408, the vertebral body implant is secured to the patient.
The vertebral body implant may be secured using the surface features
provided thereon, or through the use of, for example, a fixation system
as illustrated in FIG. 12. As noted, if a fixation system is used, the
implant is connected to a plate which is attached to healthy vertebra
using screws. Once the screws are inserted, AP and lateral X-rays are
obtained to confirm proper placement of the vertebral body implant,
screws and any other hardware.

[0071]In the embodiment of FIG. 14, at block 1410 a drug is provided to
the implant. This may include, for example, using a syringe to fill the
vertebral body implant, or connecting the vertebral body implant to drug
source such as described below with reference to FIG. 15.

[0072]At block 1412, the surgical site is closed. This may include
irrigating the area and closing the incision per standard surgical
techniques.

[0073]It would also be appreciated that the illustrative surgical method
of FIG. 14 is merely exemplary, and various modifications to the method
are within the scope of the present invention. For example, in
embodiments of the present invention, the drug may be provided to the
vertebral body implant before or after implantation. Additionally, there
are a number of methods by which drugs may be introduced to the implant,
and by which the drug flows may from the implant through the drug
delivery ports. For example, as noted above, drugs may be introduced
under pressure using a syringe to facilitate flow of drugs from the
delivery ports. In other embodiments described below, a reservoir pump
may facilitate the flow of drugs from the delivery ports. Additionally,
capillary action may be used to facilitate the flow of drugs from the
delivery ports. It would be appreciated that these examples are provided
for illustration and do not limit the embodiments of the present
invention.

[0074]Furthermore, in certain circumstances, the drug is not necessarily
provided prior to closure of the surgical site. Specifically, as
discussed above, the vertebral body implant includes a port that is
post-operatively accessible. As such, this port could be used to provide
the drug to the vertebral body implant after surgical site closure.

[0075]As noted above, bone and cartilage implants of the present invention
are configured to deliver drugs to a patient. FIG. 15 illustrates a
spinal implant system 1510 of the present invention that includes a
vertebral body implant 1500 connected to an implantable drug source 1502.
Similar to the embodiments described above, vertebral body implant 1500
comprises refill ports 1522A and 1522B, as well as a plurality of
respective drug delivery ports 1520A, 1520B. As shown, a connector 1506
detachable connects refill port 1522A to the distal end of a catheter
1504 extending from drug source 1502. Catheter 1504 may comprise any
catheter now known or later developed, and connector 1506 may comprise
any device which detachably couples the catheter to refill port 1522A. In
embodiments of the present invention, drug source 1502 may include a
reservoir (not shown) and a post-operatively accessible refill port (also
not shown).

[0076]In certain embodiments of the present invention, drug source 1502 is
an active drug infusion device, such as the Medtronic SYNCHROMED
programmable pump; SYNCHROMED is registered trademark of Medtronic Inc.,
Minneapolis Minn. Such pumps typically include a drug reservoir, a
peristaltic pump to pump the drug from the reservoir, and a catheter port
to connect the source to a catheter. Such devices also typically include
a battery to power the pump, an electronic module to control the flow
rate of the pump, and possibly an antenna to permit the remote
programming or control of the pump. It should be appreciated that the
pump may be implanted in, or secured externally to, the patient.

[0077]In alternative embodiments of the present invention, drug source
1502 comprises a passive drug infusion device that does not include a
pump. In one such embodiment, drug source 1502 includes a pressurized
reservoir that delivers the drug to refill port 1540 via catheter 1504.
Such passive drug infusion devices are generally smaller and less costly
than active drug infusion devices. An example of a passive device that
may be used with embodiments of the present invention is the Medtronic
ISOMED; ISOMED is registered trademark of Medtronic Inc., Minneapolis
Minn. This device delivers a drug via a reservoir which is pressurized
with a drug to between 20-40 psi. This pressurization is provided by a
syringe capable of delivering drugs between 35-55 psi.

[0078]In embodiments of the present invention, spinal implant system 1510
is configured to release drugs in various temporal and spatial patterns
and profiles, for example, releasing a drug in a continuous or pulsatile
manner for several (e.g., 5 to 15) days and/or targeting areas of the
implant, if any, that are more conducive to bacterial growth. In further
embodiments, drug delivery ports 1520 are controllable to alter the flow
rate through the ports. Such control may be provided externally, such as
by electrical or mechanical signals, heat, etc.

[0079]While embodiments of the invention have been described with a
certain degree of particularity, it is understood that the invention is
not limited to the embodiments set forth herein for purposes of
exemplification. Modifications and variations of the specific methods and
devices described herein will be obvious to those skilled in the art from
the foregoing detailed description. Such modifications and variations do
not depart from the inventive concept and scope of the present invention
and are intended to come within the scope of the appended claims.